1. Field of the Invention
The present invention relates to an electrostatic capacitive coordinate input device for example used as a pointing device of personal computers, etc.
2. Description of the Related Art
Referring to FIG. 7, which shows a schematic diagram of a conventional coordinate input device. The coordinate input device 100 is a kind of pointing device mounted in notebook-size personal computers, etc, in which coordinates can be entered by changing electrostatic capacities.
The conventional coordinate input device 100 has: an X-electrode layer 103 composed of a plurality of X-electrodes 102 stacked on the top surface of a film substrate 101 (detecting substrate) made of a synthetic resin; and a Y-electrode layer 105 composed of a plurality of Y-electrodes 104 stacked on the rear surface of the film substrate 101, wherein the X-electrodes 102 and Y-electrodes 104 are arranged in the form of a matrix.
The X-electrode layer 103 and Y-electrode layer 105 are formed from metal patterns in the form of a matrix and the surfaces of the electrode layers are covered with insulating films 106 and 107, respectively.
Further, the coordinate input device 100 is provided with a surface sheet 108 on the side of the X-electrode layer 103, which is to be used as an operation side. The electrode layers 103, 105, insulating films 106, 107, and surface sheet 108 have the same rectangular shape in outer dimensions.
The coordinate input device 100 is also provided with a control circuit board 110 as a bottom layer on the side opposite from the surface sheet 108. The control circuit board 110 is formed with the same outer dimensions as those of the film substrate 101.
The control circuit board 110 is also provided with a control circuit 111 on the surface thereof opposite from the film substrate 101.
In the case of the conventional coordinate input device 100, a cursor or the like, which appears in the display of personal computers, etc., can be moved by electrically connecting the X-electrode layer 103 and Y-electrode layer 105 to the control circuit 111 and detecting the changes in electrostatic capacity between the X-electrode layer 103 and Y-electrode layer 105 with the control circuit 111.
However, the conventional coordinate input device 100 is opaque in the film substrate 101 and control circuit board 110. Accordingly, even when the conventional coordinate input device 100 was placed on the front surface of a liquid crystal cell (not shown), it was impossible to view images displayed on the liquid crystal cell and the like through the input device 100.
Therefore, it was also impossible to incorporate a conventional electrostatic capacitive coordinate input device 100 in a liquid crystal display device.
The invention was made in consideration of the foregoing problem. It is an object of the invention to provide a transparent electrostatic capacitive coordinate input device, which can be incorporated in a liquid crystal display device, and a liquid crystal display device with the coordinate input device.
As first means for solving the above problem, the invention provides a coordinate input device arranged to include:
an upper film substrate;
a first electrode layer formed on a rear surface of the upper film substrate;
a lower film substrate;
a second electrode layer formed on a surface of the lower film substrate, the surface facing the first electrode layer; and
a transparent dielectric film held between the upper and lower film substrates,
wherein the upper and lower film substrates and the first and second electrode layers are transparent.
In an arrangement of the coordinate input device as second means for solving the above problem, the dielectric film includes a transparent base and transparent adhesive layers respectively formed on top and bottom surfaces of the base, and the upper and lower film substrates are bonded to the dielectric film with the transparent adhesive layers.
In an arrangement of the coordinate input device as third means for solving the above problem, the upper film substrate has first and second end portions opposed to each other, the first electrode layer is formed from a plurality of drive electrode patterns extending in a direction from the first end portion of the upper film substrate to the second end portion thereof and insulated from each other, a plurality of ground patterns extending in a direction from the second end portion to the first end portion are formed between the drive electrode patterns, and the ground patterns are each electrically connected.
Further, as fourth means for solving the above problem, the invention provides a liquid crystal display device with the coordinate input device, one of the above first to third means; the liquid crystal display device is arranged to include a liquid crystal cell and the coordinate input device provided on a front surface of the liquid crystal cell.
As fifth means for solving the above problem, the liquid crystal display device according to the invention is arranged so that the liquid crystal cell and coordinate input device are housed in a housing to be integrated.
As described above, in the coordinate input device according to the invention, the upper and lower film substrates, and the first and second electrode layers are transparent, and the transparent dielectric film is held between the upper and lower film substrates. Therefore, it is possible to provide a transparent coordinate input device suitable for use in a liquid crystal display device.
In the coordinate input device according to the invention, the dielectric film includes a transparent base and transparent adhesive layers respectively formed on top and bottom surfaces of the base, and the upper and lower film substrates are bonded to the dielectric film with the transparent adhesive layers. Therefore, it is possible to provide a coordinate input device with a superior transparency.
Since a plurality of ground patterns extending in a direction from the second end portion to the first end portion are formed between the drive electrode patterns and each electrically connected, only one length of lead pattern is used to connect the ground patterns and therefore a space can be used efficiently.
Further, since each of the ground patterns is located between the drive circuit patterns, a stray capacitance which arises between the drive circuit patterns can be reduced. This makes it possible to detect the changes in electrostatic capacity between the X-electrode pattern and Y-electrode pattern with high accuracy.
Further, the invention provides a liquid crystal display device with the coordinate input device, one of the above first to third means; the liquid crystal display device is arranged to include a liquid crystal cell and the coordinate input device provided on a front surface of the liquid crystal cell. This makes it possible to view images displayed on the liquid crystal cell through the transparent coordinate input device and to enter a desired coordinate directly through an operation on the liquid crystal display device, and therefore a liquid crystal display device with good operability can be provided.
Additionally, since the liquid crystal cell and coordinate input device are housed in a single housing to be integrated, a portable liquid crystal display device with a coordinate input device integrated thereinto can be provided.